Manufacturers commonly bend, shape, and cut workpieces with machine presses, press brakes, and punch presses. These, and other force engines, are collectively referred to herein as “presses”. As shown in FIG. 1, a press 10 typically includes a hydraulically driven ram 14 configured to move relative to a bed 18. The ram 14 usually moves along a vertical or horizontal axis toward and away from the bed 18. Conventionally, presses 10 shape workpieces with a set of tools and/or dies that may be coupled to the ram 14 and the bed 18. The press 10 of FIG. 1 includes a tool 22 coupled to the ram 14 and a tool 26 coupled to the bed 18. Exemplary workpieces that may be cut, bent, or otherwise formed include sheet metal and other industrial materials.
The press 10, having the vertically displaceable ram, bends a workpiece according to the following exemplary forming process. First, the ram 14 is lifted to an elevated position. Next, the workpiece is placed on the tool 26. After the workpiece is properly positioned, the ram 14 is released from the elevated position. Releasing the ram 14 initiates a downstroke of the press 10 so that the ram 14 and the tool 22 move toward the bed 18 and the tool 26. As the ram 14 moves toward the bed 18, the tool 22 presses the workpiece against the tool 26 to bend, shape, or form the workpiece. At the completion of the downstroke, the ram 14 is lifted again to the elevated position. The formed workpiece may then be removed from the press 10 by either a user or a machine. Some high speed presses may repeat the forming process at a rate of approximately two hundred cycles per minute.
A rotary bending device is a tool that may be coupled to the ram 14 of the press 10. Rotary bending devices are useful for bending a portion of a workpiece, referred to as a skirt, relative to a remainder of the workpiece. The skirt is a strip of material that stiffens the workpiece when bent relative to the remainder of the workpiece. Forming a skirt on the workpiece may be the first of a number of steps involved in hemming the workpiece.
Rotary bending devices include a saddle and a rocker. The saddle is connected to the ram 14, and the rocker is rotatably supported within the saddle. During a downstroke of the press 10, the rocker is forced into contact with the workpiece to bend the skirt. In particular, as the rotary bending device approaches the workpiece, the rocker contacts the workpiece and begins to rotate. Continued movement of the ram 14 toward the workpiece causes the rotation of the rocker to bend the skirt to a predetermined angle with respect to the remainder of the workpiece. The magnitude of the predetermined angle depends on the characteristics of the rocker.
Depending on the end use of the workpiece, it may be desirable to bend the skirt very close to the remainder of the workpiece with a single stroke of the press 10. Known rotary bending devices, however, have a limited minimum predetermined angle. Specifically, many known rotary benders, bend the skirt to within ninety degrees) (90°) of the remainder of the workpiece without difficulty, because the rocker is easily lifted from the formed workpiece on the upstroke of the ram 14 for predetermined angles ranging from one hundred eighty degrees) (180° to ninety degrees) (90°). If, however, the predetermined angle is less than ninety degrees) (90°), overlap between the rocker and the workpiece may cause the rocker to drag against the skirt on the upstroke of the ram 14. The dragging rocker may undesirably deform or mar the skirt. The potential for deforming the skirt increases in response to an increased amount of overlap between the rocker and the workpiece. Stated differently, the potential for deforming the skirt increases in response to a decreased angle between the skirt and the remainder of the workpiece. Therefore, a rotary bending device capable of bending a skirt on a workpiece without deforming the workpiece is desirable.